Improvement in rock-drills



i the same.

' "JOSEPH HANRAHAN, or OTTAWA, CANADA.

IMPROVEMENT INVRocK-DRILLS.

Specification forming part of batters Patent 158,704, dated January 12, 1875; application tiled f December 1e, 1814.

To all 4whom it may concern:

Be it known that I, JOSEPH HANRAHAN, of

` the city of Ottawa, in the county of Carleton,

in the Province of Ontario, Canada, have invented certain new and useful Improvements in Rock-Drills; and ,I do hereby declare that i the following is-a full, clear, and 'exact-depurpose when used withl a drilling-rnachine;

and it consists in beveling one or both wings `of a drill having a cruciforin 4head or bit on opposite sides unequally, whereby the cuttingedges do not intersect centrally, thennequalv beveling of the sides throwing the wing-edges out of a radial line with each other, and the incline of -thegreater bevel causes the drill I 'to rotate'ii that direction.

The through cutting-edge may be `recessed centrally to cause the' drill to form a raised center in the rock,

' about which it turns axially, and helps to direct the' drill in a straight course. n Figure 1 is an elevation of a drill embody-` ing my invention. Fig. 2 is an end view of V' Ehe drill-head is of cruciformshape. A

.I designate as the through cutting-edge,

and those at right angles 'thereto the wings C and D. Itwill'lie observedthat the cuttingedges of the wings() and D are parallel, and are not in radia.l line with each other. This results ,from the vbevel or set-off being greater on one side of the wing than'on the opposite side. rJlhe object in beveling the wings C and D in this manner is to cause the greater or broader inclines to act uniformly in one direction, whereby the drill, by ini-v pingement with the rock, turns around its axis ot' motion, andthereby at each successive impingement to cut upon a new surface.. It will, therefore, be evident that the drill can be made to perforiua revolution toward the right or left by having the greater or broader.

inclines of the bevels'in the direction the drill is required to turn.

In the construction of my ilnproved drill, I prefer to recess the cutting-edge A centrally, or between the intersecting wings O and l),-

the object being to. cause the drill by such re- A vbeveled unequally on opposite sides, as shown,

to throwthe two cutting-edges out ot' a radial line, substantially as set forth.

' 2. A rock-drill having either'or both of its radial wings beveled uuequally on opposite sides, and its through cutting-edge A recessed centrally, as and for the purpose .set forth.

. JOSEPH HANRAHAN.

' Witnesses:

J oHN Gnrsr, Jr., HENRY Garsr. 

